In recent years, mobile phones have been widely used. Early mobile phones have been mainly in the form of a vertically long plate; however, recently, in order to reduce the length of a mobile phone for increasing the portability, a folding mobile phone is becoming mainstream, of which casing is divided into an upper casing and a lower casing overlapping each other so that the casing can be folded and unfolded with respect to a rotary shaft mounted on one side of the upper and the lower casings.
Furthermore, Japanese Laid-open Patent Publication No. 2001-265507 discloses a mobile terminal device operable by a jog dial. The mobile terminal device has a fingerprint authentication function integrated with the jog dial, and restricts or allows a terminal operation function using the jog dial depending on a result of fingerprint matching.
Recently, a device that can perform fingerprint authentication and a pointing operation by using a fingerprint sensor device mounted on a mobile terminal or the like is increasing.
The pointing operation normally tends to be activated in any situations.
Although it depends on where the fingerprint sensor is mounted, there is often the case that the fingerprint sensor is unintentionally touched with a finger because of the way of carrying or holding the mobile terminal independently of operations. When the finger-touch is performed unintentionally (even when it is light touch), the fingerprint sensor senses the contact of the finger and outputs operational information.
In the case of the unintentional contact, there is a tendency that the grounding to a sensor unit of the fingerprint sensor becomes unstable and feature data of the finger significantly varies, so that a malfunction or a false operation continuously occurs in a higher-level application (e.g., full browser), which is a problem.